Under normal circumstances, there is no limit to the number of 4D ultrasound exams a pregnant woman can have during her pregnancy. Because 4D ultrasound is a non-invasive and non-invasive imaging method, it is not harmful to both the pregnant woman and the fetus. It is best for pregnant women to have 3-4 4D ultrasound examinations from pregnancy to delivery. The first examination can determine whether there is an early pregnancy and the number of fetuses in the pregnancy, and the next three should be chosen between the 12th and 16th weeks of pregnancy, between the 20th and 25th weeks and between the 37th and 40th weeks of pregnancy, respectively. This is based on the doctor’s need to observe and monitor the growth and development of the fetus through three systematic ultrasound examinations.